drm/i2c: tda998x: split tda998x_encoder_dpms into enable/disable

This fits better with the drm_bridge callbacks for when this
driver becomes a drm_bridge.
Suggested-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Signed-off-by: Peter Rosin <peda@axentia.se>
[edited by rmk to just split the tda998x_encoder_dpms() function
 and restore the double-disable protection we originally had,
 preserving original behaviour.]
Tested-by: Peter Rosin <peda@axentia.se>
Signed-off-by: Russell King <rmk+kernel@armlinux.org.uk>

drivers/gpu/drm/i2c/tda998x_drv.c

@@ -1308,18 +1308,9 @@ static int tda998x_connector_init(struct tda998x_priv *priv,
 
 /* DRM encoder functions */
 
-static void tda998x_encoder_dpms(struct drm_encoder *encoder, int mode)
+static void tda998x_enable(struct tda998x_priv *priv)
 {
-	struct tda998x_priv *priv = enc_to_tda998x_priv(encoder);
-	bool on;
-
-	/* we only care about on or off: */
-	on = mode == DRM_MODE_DPMS_ON;
-
-	if (on == priv->is_on)
-		return;
-
-	if (on) {
+	if (!priv->is_on) {
 		/* enable video ports, audio will be enabled later */
 		reg_write(priv, REG_ENA_VP_0, 0xff);
 		reg_write(priv, REG_ENA_VP_1, 0xff);
@@ -1330,7 +1321,12 @@ static void tda998x_encoder_dpms(struct drm_encoder *encoder, int mode)
 		reg_write(priv, REG_VIP_CNTRL_2, priv->vip_cntrl_2);
 
 		priv->is_on = true;
-	} else {
+	}
+}
+
+static void tda998x_disable(struct tda998x_priv *priv)
+{
+	if (priv->is_on) {
 		/* disable video ports */
 		reg_write(priv, REG_ENA_VP_0, 0x00);
 		reg_write(priv, REG_ENA_VP_1, 0x00);
@@ -1340,6 +1336,23 @@ static void tda998x_encoder_dpms(struct drm_encoder *encoder, int mode)
 	}
 }
 
+static void tda998x_encoder_dpms(struct drm_encoder *encoder, int mode)
+{
+	struct tda998x_priv *priv = enc_to_tda998x_priv(encoder);
+	bool on;
+
+	/* we only care about on or off: */
+	on = mode == DRM_MODE_DPMS_ON;
+
+	if (on == priv->is_on)
+		return;
+
+	if (on)
+		tda998x_enable(priv);
+	else
+		tda998x_disable(priv);
+}
+
 static void
 tda998x_encoder_mode_set(struct drm_encoder *encoder,
 			 struct drm_display_mode *mode,